Plasma monitoring method and semiconductor production apparatus

ABSTRACT

In certain embodiments a plasma is supplied from a plasma chamber  10  into a reaction chamber  18  of a plasma CVD apparatus. An electrode  22  is disposed in the reaction chamber  18 . A semiconductor wafer on which a thin film is to be formed is placed on the electrode  22 . A radio-frequency wave is generated by a radio-frequency wave generator  28  and supplied to the electrode  22  via a radio-frequency matching network  30 , a blocking capacitor  32 , and an RF probe  34  so as to control the plasma in the plasma chamber  10 . A judgment device  38  is electrically connected to the RF probe  34 . The voltage and current are be measured by the RF probe and the judgment device  38  is used to judge the state of the plasma in the plasma chamber  10.

TECHNICAL FIELD

The present invention relates to methods of judging the state of aplasma used in a process of producing a semiconductor device and also tosemiconductor production devices including mechanisms for judging thestate of the plasma.

RELATED ART

Processes of producing a semiconductor device often include a process offorming a thin film on a semiconductor substrate. Chemical vapordeposition, sputtering, or other similar processes using a plasma may beemployed as the mean for forming the thin film. To form a high-qualitythin film, it is required to maintain the plasma in a particular state.To this end, it is important to precisely judge the state of the plasmaused in the chemical vapor deposition process or the sputtering process.

SUMMARY

One embodiment of the present invention relates to an apparatus forproducing a semiconductor device by generating or controlling a plasmausing a radio-frequency wave. The semiconductor production apparatusincludes radio-frequency wave generation means for generating theradio-frequency wave and an electrode disposed in a space where theplasma is generated. The apparatus also includes radio-frequency wavepropagation means for propagating the radio-frequency wave generated bythe radio-frequency wave generation means to the electrode.Radio-frequency voltage measurement means are positioned to measure thevoltage of the radio-frequency wave propagating through theradio-frequency wave propagation means, and radio-frequency currentmeasurement means are positioned to measure the current of theradio-frequency wave propagating through the radio-frequency wavepropagation means. Judgment means are provided for judging the state ofthe plasma on the basis of the voltage and the current.

Another embodiment relates to a method of monitoring a plasma in aprocess of generating or controlling plasma using a radio-frequencywave. The method includes measuring the voltage and the current of theradio-frequency wave and judging the state of the plasma on the basis ofthe voltage and the current.

Still another embodiment relates to an apparatus for semiconductordevice fabrication using a plasma, the apparatus including a plasmachamber having a plasma formation region. At least one generator isprovided to supply energy to the plasma formation region. The apparatusalso includes at least one voltage measurement device and at least onecurrent measurement device.

Another embodiment relates to an apparatus for semiconductor devicefabrication using a plasma and including a chamber having a plasmaformation region. A generator and a conduit to deliver energy from thegenerator to the plasma formation region are provided. The apparatusalso includes a voltage measurement device and a current measurementdevice.

Another embodiment relates to a method for monitoring a plasma during aplasma processing operation. The method includes measuring a voltage anda current in a signal. The method also includes detecting a change in atleast one of the voltage and current.

Another embodiment relates to a method for monitoring a plasma during aplasma processing operation using RF energy. The method includesmonitoring a voltage of an RF signal and monitoring a current of the RFsignal. The method also includes detecting a first to change of thevoltage and the current.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described with reference to theaccompanying drawings which, for illustrative purposes, are schematicand not drawn to scale.

FIG. 1 is a schematic diagram of a first embodiment of a semiconductorproduction device according to the present invention.

FIG. 2 is a circuit diagram of an RF probe used in the first embodimentof the semiconductor production device according to the presentinvention.

FIG. 3 is a schematic diagram of a second embodiment of a semiconductorproduction device according to the present invention.

FIG. 4 is a schematic diagram of a third embodiment of a semiconductorproduction device according to the present invention.

DETAILED DESCRIPTION

Certain embodiments of the present invention relate to methods anddevices for determining the state of a plasma during a plasma operationsuch as, for example, a deposition operation. In a system utilizing anRF power, this may be accomplished by measuring the voltage and currentduring the plasma operation and observing when changes to the voltageand/or current occur. Changes in the voltage and/or the current mayprovide an indication of the state of the plasma during the operation.Embodiments of the present invention may be preferably applied to asemiconductor production apparatus in which chemical vapor deposition orsputtering is performed using a plasma.

According to an aspect of certain embodiments of the present invention,there is provided a semiconductor production apparatus for producing asemiconductor device by generating or controlling a plasma using aradio-frequency wave. The semiconductor production apparatus includes aradio-frequency wave generation means for generating radio-frequencywaves and an electrode disposed in a space where the plasma isgenerated. The apparatus also includes radio-frequency wave propagationmeans for propagating the radio-frequency waves generated by theradio-frequency wave generation means to the electrode. The apparatusalso includes radio-frequency voltage measurement means, for measuringthe voltage of the radio-frequency waves propagating through theradio-frequency wave propagation means, and radio-frequency currentmeasurement means, for measuring the current of the radio-frequencywaves propagating through the radio-frequency wave propagation means.Judgment means for judging the state of the plasma on the basis of thevoltage and the current are also included in the apparatus.

There is a possibility that a change occurs only in either the voltageor the current of the radio-frequency wave when the state of the plasmachanges. Therefore, in the semiconductor production apparatus accordingto certain embodiments of the present invention, both the voltage andcurrent of the radio-frequency wave are monitored to judge the state ofthe plasma. More specifically, when a change occurs in a plasma during aprocess of forming a thin film by means of chemical vapor depositionusing the plasma, there is a possibility that no change occurs in thevoltage of the radio-frequency wave or there is a delay in the change inthe voltage. In this case, if only the voltage is monitored, the stateof the plasma cannot be correctly judged. When only the current ismonitored, a similar problem can occur. In view of the above, both thevoltage and current of the radio-frequency wave are monitored and thestate of the plasma is precisely judged on the basis of the monitoredresult.

Herein, the change in the voltage or current of the radio-frequency waverefers to, for example, a change at the beginning, a change during aparticular period, and a change at the end. The changes in the voltageand the current may be determined taking into account thecharacteristics of a material to be etched.

According to certain embodiments, the judgment means preferably judgesthe state of the plasma on the basis of either the voltage or thecurrent, whichever has changed earlier than the other.

Furthermore, it is preferable that the radio-frequency wave propagationmeans be only one electric device which exists between the electrode andmeasurement means including the radio-frequency voltage measurementmeans and the radio-frequency current measurement means. This is becauseif there is a radio-frequency matching network or a blocking capacitorbetween the electrode and the measurement means, such an electric devicecan cause degradation in measurement accuracy of the voltage or thecurrent of the radio-frequency wave. However, an electric device isallowed to be disposed between the electrode and the measurement meansif the electric device does not cause degradation in measurementaccuracy of the voltage or the current of the radio-frequency wave.

Preferably, the radio-frequency current measurement means measures acurrent flowing through a coil wound around the radio-frequency wavepropagation means. This is desirable because the current flowing throughthe radio-frequency wave propagation means does not pass directlythrough the radio-frequency current measurement means and thus theradio-frequency current measurement means is not heated and no changeoccurs in plasma impedance. If the current of the radio-frequency waveflowing through the radio-frequency wave propagation means is directlymeasured, the above-described problems will occur.

According to another aspect the present invention, embodiments include amethod of monitoring a plasma in a process of generating or controllingthe plasma using a radio-frequency wave. The method includes measuringthe voltage and the current of the radio-frequency wave, and judging thestate of the plasma on the basis of the voltage and the current. In thisplasma monitoring method, because the state of the plasma is judged onthe basis of the voltage and the current of the radio-frequency waves,it is possible to make a precise judgment on the state of the plasma forthe same reason described above with reference to the semiconductorproduction apparatus according to the present invention.

In the plasma monitoring method according to a preferred embodiment thepresent invention, the state of the plasma is judged on the basis ofeither the voltage or current, whichever has changed earlier than theother.

In the case where a plurality of electrodes are disposed in a spacewhere a plasma is generated and a radio-frequency wave is applied toeach electrode, it is preferable that radio-frequency voltagemeasurement means and radio-frequency current measurement means beprovided on each radio-frequency wave propagation means electricallyconnected to each electrode so that the judgment can be made using agreater amount of data and thus the state of the plasma can be judgedmore precisely.

In the case where a radio-frequency wave is applied to an electrode anda radio-frequency wave is also applied to an induction coil, it ispreferable that: (1) radio-frequency voltage measurement means andradio-frequency current measurement means be provided on theradio-frequency wave propagation means electrically connected to theelectrode, and (2) radio-frequency voltage measurement means andradio-frequency current measurement means be also provided on theradio-frequency wave propagation means electrically connected to theinduction coil, for the same reason described above in connection withthe case where the plurality of electrodes are disposed in the spacewhere the plasma is generated.

Several preferred embodiments of devices and methods will be describedin detail with reference to the attached drawings.

FIG. 1 is a schematic diagram of a first embodiment of a semiconductorproduction device according to the present invention. In this firstembodiment, the invention is applied to an ECR plasma CVD apparatus.

Gas such as Ar or O₂ used to generate a plasma is supplied into a plasmachamber 10 via a gas inlet pipe 12. A main coil 14 is disposed aroundthe plasma chamber 10. A radio-frequency wave is applied to the plasmachamber 10.

A plasma is generated in the plasma chamber 10 and supplied into areaction chamber 18. Reaction gas such as SiH₄ is supplied into thereaction chamber 18 via a gas inlet pipe 20. An electrode 22 is disposedin the reaction chamber 18. On the electrode 22, a semiconductor waferis placed on which a thin film is to be deposited using the ECR plasmaCVD apparatus. There is also provided an auxiliary coil 24.

A radio-frequency wave is generated by a radio-frequency wave generator28 electrically connected to a ground 26. The generated radio-frequencywave is applied to the electrode 22 via a radio-frequency matchingnetwork 30, a blocking capacitor 32, and an RF probe 34, so as tocontrol the plasma in the plasma chamber 10. These electric devices maybe electrically connected in a series fashion via a lead line orinterconnection wire 36 which is employed by example as theradio-frequency wave propagation means.

The RF probe 34 is an example of the measurement means including theradio-frequency voltage measurement means and the radio-frequencycurrent measurement means. In this structure, the interconnection wire36 is preferably the only electric device which exists between theelectrode 22 and the RF probe 34.

The RF probe 34 is electrically connected to a judgment device 38. Thejudgment device 38 is an example of the judgment means. Of the voltageand the current of the radio-frequency wave measured by the RF probe 34,whichever has changed earlier may be used to judge the state of theplasma in the plasma chamber 10.

FIG. 2 is a circuit diagram of an embodiment of the RF probe 34. A coil40 wound around the interconnection wire 36 is electrically connected toan ammeter 42. The ammeter 42 and the coil 40 form a current measuringdevice. The current measuring device is an example of theradio-frequency current measurement means. The interconnection wire 36is electrically connected to a circuit 44 consisting of resistors andcapacitors. The circuit 44 and a volt meter 46 form a voltage measuringdevice. The voltage measuring device is an example of theradio-frequency voltage measurement means.

The voltage and the current of the radio-frequency wave are measuredwith the RF probe 34 during the process of forming the thin film on thesemiconductor using the plasma CVD apparatus. On the basis of either thevoltage or the current which has changed earlier than the other, thejudgment device 38 judges the state of the plasma in the plasma chamber10. This technique allows the state of the plasma to be judgedprecisely.

FIG. 3 is a schematic diagram of a second embodiment of a semiconductorproduction device according to the present invention. In this secondembodiment, the invention is applied to an ICP plasma CVD apparatus.

A cathode electrode 52 is disposed on the bottom of a reaction chamber50. On the cathode electrode 52, a semiconductor wafer is placed onwhich a thin film is to be deposited using this plasma CVD apparatus. Ananode electrode 54 is disposed at the top of the reaction chamber 50. Aninduction coil 56 is disposed around the reaction chamber 50.

The cathode electrode 52 is electrically connected to an RF probe 58, ablocking capacitor 60, a radio-frequency matching network 62, and aradio-frequency wave generator 64. The induction coil 56 is electricallyconnected to an RF probe 66, a blocking capacitor 68, a radio-frequencymatching network 70, and a radio-frequency wave generator 72. The RFprobes 58 and 66 are electrically connected to a judgment device 74.

The RF probes 58 and 66 are examples of the measurement means includingthe radio-frequency voltage measurement means and the radio-frequencycurrent measurement means. The RF probe 58 electrically connected to thecathode electrode 52 serves as a main probe and the RF probeelectrically connected to the induction coil 56 serves as an auxiliaryprobe. The RF probes 58 and 66 may have a similar structure to that ofthe RF probe 34 employed in the first embodiment.

In this embodiment the radio-frequency voltage and current are measuredwith the RF probes 58 and 66, and the measured data is sent to thejudgment device 74. The voltage and current measured with the RF probe58 serving as the main probe are used as main data and the voltage andcurrent measured with the RF probe 66 serving as the auxiliary probe areused as auxiliary data. Using these data, the state of the plasma in thereaction chamber 50 is judged. Thus, in this second embodiment, thejudgment is made using a greater number of data than in the firstembodiment. This allows the state of the plasma in the reaction chamber50 to be judged in a more precise fashion.

The present invention may be applied not only to plasma CVD apparatus ofthe types described above with reference to the first and secondembodiments, but also to any type of plasma CVD apparatus usingradio-frequency waves.

FIG. 4 is a schematic diagram of a third embodiment of a semiconductorproduction device according to the present invention. In this thirdembodiment, the invention is applied to a sputtering apparatus with abias via RF-DC coupling.

Electrodes 82 and 84 are disposed in a chamber 80 such that they faceeach other. On the electrode 82, a semiconductor wafer is placed onwhich a thin film is to be deposited using this sputtering apparatus. Atarget is placed on the electrode 84. A magnet 86 is placed at the backof the electrode 84.

The electrode 84 is electrically connected to an RF probe 88, a blockingcapacitor 90, a radio-frequency matching network 92, and aradio-frequency wave generator 94. The RF probe 88 is electricallyconnected to a judgment device 100. An interconnection wire via whichthe RF probe 88 and the blocking capacitor 90 are electrically connectedto each other is electrically connected to a DC power supply 98 via ahigh-frequency filter 96.

A capacitor 102 may be electrically connected to the electrode 82. Aninterconnection wire via which the electrode 82 and the capacitor 102are electrically connected to each other may be electrically connectedto a DC power supply 106 via a high-frequency filter 104.

Ar gas which is discharged by a radio-frequency wave into a plasma stateis supplied into the chamber 80 via a gas inlet pipe 108.

The RF probe 88 may have a similar structure to that of the RF probe 34employed in the first embodiment. In this third embodiment, the voltageand the current of the radio-frequency wave are measured with the RFprobe 88 during the process of forming the thin film on thesemiconductor using the sputtering apparatus. On the basis of either thevoltage or the current which has changed earlier than the other, thejudgment device 100 judges the state of the plasma in the chamber 80.This technique allows the state of the plasma to be judged precisely.

The present invention may be applied not only to sputtering apparatus ofthe type described above with reference to the third embodiment, butalso to any type of sputtering apparatus in which a plasma is generatedor controlled using a radio-frequency signal.

Embodiments of the present invention may include a variety of plasmasystem configurations using radio-frequency Hertzian waves.

Although in the first, second, and third embodiments described above,the state of the plasma is judged on the basis of either the voltage orcurrent of the radio-frequency wave which has changed earlier than theother, the voltage or current which has change later than the other maybe employed to judge the state of the plasma so as to avoid incorrectjudgment caused by noise. When either the voltage or current which haschanged earlier than the other is employed, there is a possibility thatthe employed value includes a numerical error due to noise. Such aproblem can be avoided by performing the judgment when a subsequentchange occurs in the current if the voltage has changed earlier or whena subsequent change occurs in the voltage if the current has changedearlier.

In certain preferred embodiments, the signal from a generator is coupledto the chamber through a conduit which permits the monitoring of bothvoltage and current, so that variations in the plasma can be determinedfrom changes in the voltage and/or current. A variety of devices andmethods for supplying and delivering the energy to the plasma and formonitoring the voltage and current may be utilized. By determiningchanges in the state of the plasma quickly and accurately, embodimentsof the present invention can lead to better process control.

It will, of course, be understood that modifications of the presentinvention, in its various aspects, will be apparent to those skilled inthe art. Other embodiments are possible, their specific featuresdepending upon the particular application. For example, a variety ofchamber and sputtering configurations using may be employed in additionto those discussed above. In addition, other types of circuitry andmeasuring devices could be utilized. Therefore, the scope of theinvention should not be limited by the particular embodiments hereindescribed.

What is claimed:
 1. An apparatus for producing a semiconductor device bygenerating or controlling a plasma using a radio-frequency wave, thesemiconductor production apparatus comprising: radio-frequency wavegeneration means for generating the radio-frequency wave; an electrodedisposed in a space where the plasma is generated; radio-frequency wavepropagation means for propagating the radio-frequency wave generated bythe radio-frequency wave generation means to the electrode;radio-frequency voltage measurement means positioned to measure thevoltage of the radio-frequency wave propagating through theradio-frequency wave propagation means; radio-frequency currentmeasurement means positioned to measure the current of theradio-frequency wave propagating through the radio-frequency wavepropagation means; and judgment means for judging the state of theplasma on the basis of the voltage and the current, wherein the judgmentmeans judges the state of the plasma on the basis of the first to changeof the voltage and the current.
 2. A semiconductor production apparatusaccording to claim 1, wherein measurement means comprises theradio-frequency voltage measurement means and the radio-frequencycurrent measurement means, and the radio-frequency wave propagationmeans is the only electric device which exists between the electrode andthe measurement means.
 3. A semiconductor production apparatus accordingto claim 1, wherein chemical vapor deposition or sputtering is performedusing the plasma.
 4. A semiconductor production apparatus according toclaim 1, wherein the radio-frequency current measurement means measuresa current flowing through a coil wound around the radio-frequency wavepropagation means.
 5. A semiconductor production apparatus according toclaim 1, wherein the coil comprises a multi-turn coil.
 6. An apparatusfor semiconductor device fabrication using a plasma, the apparatuscomprising: a plasma chamber having a plasma formation region; at leastone RF generator to supply energy to the plasma formation region; atleast one RF voltage measurement device; at least one RF currentmeasurement device; and a device to compare any changes in voltage andcurrent and determine the order of the changes.
 7. An apparatus forsemiconductor device fabrication according to claim 6, wherein the RFcurrent measurement device comprises a coil surrounding a portion of thelead line and an ammeter coupled to the coil.
 8. An apparatus as inclaim 6, further comprising: an electrode to deliver energy from the RFgenerator to the plasma formation region; a lead line coupling the RFgenerator to the electrode; and an RF matching network and a blockingcapacitor coupled to the lead line, wherein the apparatus is arranged sothat an RF signal travels from the RF generator through the RF matchingnetwork, the blocking capacitor, the RF probe and the electrode.
 9. Anapparatus as in claim 6, further comprising: at least one electrode todeliver energy from the RF generator to the plasma formation region,wherein the at least one electrode includes a first electrode and asecond electrode, and wherein the first electrode is coupled to the RFgenerator; a first DC power supply; a first high frequency filter; thefirst DC power supply coupled to the first electrode through the firsthigh frequency filter; a second DC power supply; and a second highfrequency filter; the second DC power supply coupled to the secondelectrode through the second high frequency filter.
 10. An apparatus asin claim 9, wherein the at least one RF voltage measurement deviceincludes a first voltage measurement device electrically connected tothe first electrode and a second voltage measurement device electricallyconnected to the second electrode, and the at least one RF currentmeasurement device includes a first current measurement deviceelectrically connected to the first electrode and a second currentmeasurement device electrically connected to the second electrode. 11.An apparatus as in claim 10 wherein the device to compare any changes involtage and current and determine the order of the changes alsodetermines the state of a plasma formed in the plasma formation regionbased on only one of the voltage and current.
 12. A plasma processingapparatus comprising: a plasma chamber having a plasma formation region;at least one RF generator to supply energy to the plasma formationregion; at least one RF voltage measurement device to measure voltage;at least one RF current measurement device to measure current; and ajudgement device in communication with the voltage measurement deviceand the current measurement device, that determines the state of aplasma formed in the plasma formation region based on the change in onlyone of the voltage and current.
 13. An apparatus as in claim 12, whereinthe judgement device determines the state of the plasma based on thefirst to change of the voltage and current.
 14. An apparatus as in claim12, wherein the judgement device determines the state of the plasmabased on the second to change of the voltage and current.
 15. A plasmaprocessing apparatus comprising: a plasma chamber having a plasmaformation region; at least one RF generator to supply energy to theplasma formation region; at least one RF voltage measurement device tomeasure voltage; at least one RF current measurement device to measurecurrent; and a judgement device that determines the first to change ofthe voltage and current.
 16. An apparatus as in claim 15, wherein thejudgement device further determines the state of the plasma based ononly one of the voltage and current.
 17. An apparatus as in claim 15,wherein the judgement device further determines the state of the plasmabased on the first to change of the voltage and current.